In a simple example below I try to write an equation with an unknown value present among other values that have unit, but I get an error since the unknown value d does not have a unit yet.

How to write such expressions, e.g. for use in solve later?

In the code below the new function g is defined based on existing function f, but the new function g is then dependent on f at the time of definition, which is shown since later changes to f will change value of g.

How to fix definition of g based on f at the when g is defined, so later changes of f does not alter g ?

Can anybody recommend a good general reference book or cookbook for Maple (2016), that shows the most used and useful commands, and ways to do general operations?

Below I try to use units for a simple expression, where "m" and "mm" is added on Windows using Ctrl-Shift-U.

Why does the value with unit "1 [[m]]" not show as "1 m" in (1), but simply as "m" ?

Why does the addition not result in "2 m" ?

At least I had expected the addition to be made when using "evalf()".

Below is a custom distribution created based on a function that takes a parameter.

It is possible to create the custom distribution e.g. as D1 and then use it afterwards to find e.g. Mean, but it is not possible to call Mean directly with the creation of the distribution in the call.

Why is that ?